This pisper explores the potential application of ABC in a situation of rapid change - the introduction of markets for health care in the UK. This changing environment places pressures on hospital units to refine their costing methods for product costing, budget construction and the pursuit of efficiency. These are areas of management accounting for which activity-based costing (ABC) has been proposed as a refinement to traditional costings. The merits of the ABC approach were examined by conducting four case studies of acute hospitatls. The results cast doubt on the benefits to be gained from ABC in product costing, but revealed potential applications in its wider roles of cost reduction and budget construction.